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Hawaiian Islands Synoptic Discussion and Guidance

164
FXHW60 PHFO 240630
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST WED JUL 23 2014

.SYNOPSIS...
TRADE WINDS REMAIN MODERATE TO LOCALLY BREEZY TONIGHT AND
THURSDAY...THEN DIMINISHING SLIGHTLY DURING THE UPCOMING WEEKEND.
BRIEF WINDWARD SHOWERS WILL CONTINUE DURING THE NEXT COUPLE OF
DAYS...THEN WINDWARD SHOWERS WILL INCREASE TOWARDS THE LATER PART OF
THE WEEKEND AND INTO EARLY NEXT WEEK.

&&

.DISCUSSION...
STRONG SFC HIGH PRESSURE FAR NNE OF THE MAIN HAWAIIAN ISLANDS WILL
KEEP MODERATE TO LOCALLY STRONG TRADE WINDS ACROSS THE AREA TONIGHT
AND ON THU WITH SHOWERS FOCUSING OVER WINDWARD AND MOUNTAIN AREAS.
THE AIRMASS OVER THE ISLANDS IS GRADUALLY BECOMING DRIER...WHILE
ATMOSPHERIC CONDITIONS CONTINUE TO BECOME MORE STABLE. 00Z SOUNDINGS
FROM LIHUE AND HILO SHOW THAT THE INVERSIONS ARE RE-ESTABLISHING
AROUND 6-8 THOUSAND FEET...ALONG WITH A DEVELOPING RIDGE ALOFT.
THIS SYNOPTIC SCENARIO WILL FAVOR A DECREASE IN SHOWER ACTIVITY
DURING THE NEXT SEVERAL DAYS...HOWEVER...ONE MORE ROUND OF ENHANCED
SHOWERS IS EXPECTED TONIGHT AS A BAND OF LOW-MID LVL CLOUDS IS
APPROACHING THE ISLANDS FROM THE NW AND SHOULD BEGIN GENERATING
MORE SHOWERS LATER THIS EVENING.

LATEST MIMIC/GLOBAL MODEL MOISTURE ANALYSES DEPICT A DRIER AIRMASS
UPSTREAM OF THE ISLANDS WHICH IS EXPECTED TO BRING A MORE TYPICAL
TRADE WIND REGIME FOR THE SEASON...DOMINATED BY WINDWARD SHOWERS
FAVORING NIGHTS AND MORNINGS...AND PERIODS OF AFTERNOON CLOUDS AND
SHOWERS OVER THE LEEWARD AREAS OF THE BIG ISLAND DURING THE NEXT
COUPLE OF DAYS. THEN BY LATE SAT AND INTO SUN MODELS SHOW A WEAK LOW
MOVING S OF THE ISLANDS AND BRINGING A SMALL INCREASE IN SHOWER
ACTIVITY...ALONG WITH POTENTIAL FOR STRONGER TRADES. THIS SCENARIO
WILL ALSO BE REINFORCED BY THE DEVELOPMENT OF WEAK TROUGHING ALOFT
AND INCREASING MOISTURE CONTENT AT THE LOW LVLS LATE IN THE WEEKEND
AND INTO EARLY NEXT WEEK.

LONG RANGE MODELS ARE ALSO DEPICTING A LARGE AREA OF TROPICAL
MOISTURE REACHING THE ISLANDS FROM THE E SOMETIME ON TUE. AND
ALTHOUGH IS TOO EARLY TO EMBRACE A DEFINITE SOLUTION FOR THE
EXTENDED FORECAST PERIOD...THE SITUATION WILL BE CLOSELY MONITORED
WITH THE FORECAST BEING ADJUSTED AS NEW MODEL DATA BECOMES
AVAILABLE.

&&

.AVIATION...
ISLAND TERMINALS SHOULD REMAIN FAIRLY QUIET TONIGHT WITH PREVAILING
VFR. PASSING SHOWERS EMBEDDED IN THE TRADE WIND FLOW MAY CARRY BRIEF
MVFR CONDITIONS...MAINLY AFFECTING WINDWARD AND MAUKA AREAS.

MODERATE AND GUSTY TRADE WINDS WILL CONTINUE INTO THURSDAY AND
AIRMET TANGO REMAINS POSTED FOR LOW LEVEL TURB IN THE LEE OF THE
TERRAIN FOR ALL ISLANDS.


&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ REMAINS IN EFFECT FOR THE TYPICALLY
WINDY WATERS AROUND THE BIG ISLAND AND MAUI DUE TO FRESH TO LOCALLY
STRONG TRADE WINDS. WINDS ARE EXPECTED TO DIMINISH BELOW SCA SPEEDS
FROM FRIDAY INTO SATURDAY...AND THEN INCREASE SLIGHTLY ON SUNDAY AND
MONDAY. THERE/S AN OUTSIDE CHANCE A TROPICAL SYSTEM PASSING WELL S
OF THE ISLANDS KEEPS THE LOCAL GRADIENT TIGHTER THAN CURRENTLY
EXPECTED...WHICH WOULD LEAD TO STRONGER TRADE WINDS.

NO SIGNIFICANT SWELLS ARE EXPECTED THROUGH THE UPCOMING WEEK. SMALL
LONG-PERIOD BACKGROUND SWELL FROM THE SSW AND SHORT-PERIOD SWELL
FROM THE SE REPRESENT THE SWELL SOURCES FROM THE S HEMISPHERE...
WHILE SHORT PERIOD WIND WAVES FROM THE E REPRESENT THE ONLY SOURCE
OF SWELL FROM THE N HEMISPHERE. THE OAHU SURF DISCUSSION /SRDHFO/
HAS BEEN UPDATED AND CONTAINS DETAILS THAN CAN BE LOOSELY APPLIED
STATEWIDE.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY THROUGH 6 PM HST THURSDAY FOR THE PAILOLO
AND ALENUIHAHA CHANNELS...MAALAEA BAY AND WATERS SOUTH OF THE BIG
ISLAND.

&&

$$

DISCUSSION/MARINE...REYNES
AVIATION...WROE




Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office